From: Dave Hansen <dave.hansen@intel.com>
To: "Yu, Yu-cheng" <yu-cheng.yu@intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org,
linux-mm@kvack.org, linux-arch@vger.kernel.org,
linux-api@vger.kernel.org, Arnd Bergmann <arnd@arndb.de>,
Andy Lutomirski <luto@kernel.org>,
Balbir Singh <bsingharora@gmail.com>,
Borislav Petkov <bp@alien8.de>,
Cyrill Gorcunov <gorcunov@gmail.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
Eugene Syromiatnikov <esyr@redhat.com>,
Florian Weimer <fweimer@redhat.com>,
"H.J. Lu" <hjl.tools@gmail.com>, Jann Horn <jannh@google.com>,
Jonathan Corbet <corbet@lwn.net>,
Kees Cook <keescook@chromium.org>,
Mike Kravetz <mike.kravetz@oracle.com>,
Nadav Amit <nadav.amit@gmail.com>,
Oleg Nesterov <oleg@redhat.com>, Pavel Machek <pavel@ucw.cz>,
Peter Zijlstra <peterz@infradead.org>,
Randy Dunlap <rdunlap@infradead.org>,
"Ravi V. Shankar" <ravi.v.shankar@intel.com>,
Vedvyas Shanbhogue <vedvyas.shanbhogue@intel.com>,
Dave Martin <Dave.Martin@arm.com>,
Weijiang Yang <weijiang.yang@intel.com>,
Pengfei Xu <pengfei.xu@intel.com>,
Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v18 05/25] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states
Date: Mon, 1 Feb 2021 14:59:24 -0800 [thread overview]
Message-ID: <cd8f4889-fbe4-fc0e-0686-9c9ecc4a125b@intel.com> (raw)
In-Reply-To: <465836bd-9c80-fed9-d9af-89275ff810eb@intel.com>
On 2/1/21 2:43 PM, Yu, Yu-cheng wrote:
> On 1/29/2021 2:53 PM, Dave Hansen wrote:
>> On 1/29/21 2:35 PM, Yu, Yu-cheng wrote:
>>>> Andy Cooper just mentioned on IRC about this nugget in the spec:
>>>>
>>>> XRSTORS on CET state will do reserved bit and canonicality
>>>> checks on the state in similar manner as done by the WRMSR to
>>>> these state elements.
>>>>
>>>> We're using copy_kernel_to_xregs_err(), so the #GP *should* be OK.
>>>> Could we prove this out in practice, please?
>>>>>
>>> Do we want to verify that setting reserved bits in CET XSAVES states
>>> triggers GP? Then, yes, I just verified it again. Thanks for
>>> reminding. Do we have any particular case relating to this?
>>
>> I want to confirm that it triggers #GP and kills userspace without the
>> kernel WARN'ing or otherwise being visibly unhappy.
>
> For sigreturn, shadow stack pointer is checked against its restore token
> and must be smaller than TASK_SIZE_MAX. Sigreturn cannot set any
> MSR_IA32_U_CET reserved bits.
That would be nice to at least allude to in the changelog or comments.
>> What about the return-to-userspace path after a ptracer writes content
>> to the CET fields? I don't see the same tolerance for errors in
>> __fpregs_load_activate(), for instance.
>>
>
> Good thought. I have not sent out my revised PTRACE patch, but values
> from user will be checked for valid address and reserved bits.
Wait a sec... What about *THIS* series? Will *THIS* series give us
oopses when userspace blasts a new XSAVE buffer in with NT_X86_XSTATE?
next prev parent reply other threads:[~2021-02-01 22:59 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-27 21:24 [PATCH v18 00/25] Control-flow Enforcement: Shadow Stack Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 01/25] Documentation/x86: Add CET description Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 02/25] x86/cet/shstk: Add Kconfig option for user-mode control-flow protection Yu-cheng Yu
2021-01-29 19:42 ` Dave Hansen
2021-01-29 19:58 ` Andy Lutomirski
2021-01-29 20:33 ` Dave Hansen
2021-01-29 20:46 ` Borislav Petkov
2021-01-29 21:13 ` Yu, Yu-cheng
2021-01-29 20:00 ` Yu, Yu-cheng
2021-01-27 21:25 ` [PATCH v18 03/25] x86/cpufeatures: Add CET CPU feature flags for Control-flow Enforcement Technology (CET) Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 04/25] x86/cpufeatures: Introduce X86_FEATURE_CET and setup functions Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 05/25] x86/fpu/xstate: Introduce CET MSR and XSAVES supervisor states Yu-cheng Yu
2021-01-29 21:00 ` [NEEDS-REVIEW] " Dave Hansen
2021-01-29 22:35 ` Yu, Yu-cheng
2021-01-29 22:53 ` Dave Hansen
2021-02-01 22:43 ` Yu, Yu-cheng
2021-02-01 22:59 ` Dave Hansen [this message]
2021-02-01 23:05 ` Yu, Yu-cheng
2021-02-01 23:12 ` Dave Hansen
2021-02-01 23:14 ` Yu, Yu-cheng
2021-01-27 21:25 ` [PATCH v18 06/25] x86/cet: Add control-protection fault handler Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 07/25] x86/mm: Remove _PAGE_DIRTY from kernel RO pages Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 08/25] x86/mm: Introduce _PAGE_COW Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 09/25] drm/i915/gvt: Change _PAGE_DIRTY to _PAGE_DIRTY_BITS Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 10/25] x86/mm: Update pte_modify for _PAGE_COW Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 11/25] x86/mm: Update ptep_set_wrprotect() and pmdp_set_wrprotect() for transition from _PAGE_DIRTY to _PAGE_COW Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 12/25] mm: Introduce VM_SHSTK for shadow stack memory Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 13/25] x86/mm: Shadow Stack page fault error checking Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 14/25] x86/mm: Update maybe_mkwrite() for shadow stack Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 15/25] mm: Fixup places that call pte_mkwrite() directly Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 16/25] mm: Add guard pages around a shadow stack Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 17/25] mm/mmap: Add shadow stack pages to memory accounting Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 18/25] mm: Update can_follow_write_pte() for shadow stack Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 19/25] mm: Re-introduce vm_flags to do_mmap() Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 20/25] x86/cet/shstk: User-mode shadow stack support Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 21/25] x86/cet/shstk: Handle signals for shadow stack Yu-cheng Yu
2021-02-01 22:53 ` Dave Hansen
2021-02-01 22:58 ` Yu, Yu-cheng
2021-01-27 21:25 ` [PATCH v18 22/25] ELF: Introduce arch_setup_elf_property() Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 23/25] x86/cet/shstk: Handle thread shadow stack Yu-cheng Yu
2021-01-27 21:25 ` [PATCH v18 24/25] x86/cet/shstk: Add arch_prctl functions for " Yu-cheng Yu
2021-01-29 17:07 ` Dave Hansen
2021-01-29 18:56 ` Yu, Yu-cheng
2021-01-29 19:15 ` Dave Hansen
2021-01-29 19:53 ` Yu, Yu-cheng
2021-02-03 21:54 ` Yu, Yu-cheng
2021-02-03 22:11 ` Dave Hansen
2021-02-03 22:28 ` Yu, Yu-cheng
2021-01-27 21:25 ` [PATCH v18 25/25] mm: Introduce PROT_SHSTK " Yu-cheng Yu
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